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E39 (1997 - 2003) The BMW 5-Series (E39 chassis) was introduced in the United States as a 1997 model year car and lasted until the 2004 when the E60 chassis was released. The United States saw several variations including the 525i, 528i, 530i and 540i. -- View the E39 Wiki

This liquid summary is woefully lacking in the battery section where I don't even know how much fluid is inside the battery, nor how much people generally use to top it off.

Here's what I have so far (please improve so we all benefit):

- Battery: A fully-charged battery is 33.5% v/v sulfuric acid (4.2 Molar H2SO4, ) & pure water, aka distilled, demineralized, or deionized water (Bentley 020-23) with positive plates containing lead dioxide (PbO2) and negative plates of lead (Pb), both mixed with calcium (Ca) to minimize gassing (i.e., loss of water) and other elements (such as tin, antimony, & selenium to harden the plates and simplify manufacturing) in a polypropylene case. In the discharged state, both plates turn to lead sulfate (PbSO4) as the electrolyte loses its dissolved sulfuric acid and becomes primarily water (which can freeze in cold temperatures and the lead sulfate may form insoluble crystals which, over time, reduce the capacity of the battery if it is not recharged immediately after discharge). [Volume: unknown... please help!]. Replacement Interval: Lifetime fluid (top off only if needed). Test at 27°C/80°F by loading battery with 15 amperes for 1 minute (or just turn headlights on w/o engine running) and then perform a 1.265 specific-gravity hydrometer test of each of the six cells; and a 12.6 volt open-circuit voltage test across the battery terminals (Bentley 121-5, 121-6).

imho any good auto service will test them for free. 2 items i have though
1. no need to go through all that trouble. if a battery looses water there are other factors.
its a cheap battery
its over charging boiling the water out
or its old
a good interstate battery (for example). is maintenance free. and sealed. no need to open.
and...
2. NEVER lay your tools across a top post battery. you'll find out real quick how good or cheap that battery really is....lol
A+ for effort...

Yes, I have topped off the factory oem battery. I used distilled water, though minerals in water is not an issue in Seattle. I bought a plastic bottle at a dollar store that had a thin, angled straw that when you squeeze the bottle sent out a small stream of water. When I first bought the car (it was two years old at that point) I added about 20 cc to each cell to the fill line (meniscus). I believe I topped off once more about 3 years later, and it took perhaps 10 to 15 cc. Easy access, just remove the metal bracket/strap, peel back the stickers on top, and unscrew each cap to check.

Surprisingly, I replaced my battery in late 2006 (still working fine) with a "Werker" branded battery from Batteries Plus (manufactured by East Penn), and it has never needed water, going on 3.5 years now.

Bottom line Bluebee, what does it matter what the total capacity is? Or how much water people have added? If it needs water, fill it.

Is Interstate the brand most recommended for replacement? It might be nice to list suitable replacements in that short summary. Any others?

Quote:

Originally Posted by july865

NEVER lay your tools across a top post battery

Unfortunately for me, I have a DICE Silverline which constantly requires the "full reboot" procedure, which, in the E39, entails shorting out the + and - terminals in the car across the battery (according to Tom). That picture came from a DIY I wrote up for rebooting the DICE.

I'm trying to create the best E39 summary on the planet ... otherwise it isn't worth doing.

I added your 20cc bottle-and-straw recommendation.

Quote:

I replaced my battery in late 2006 with a "Werker" branded battery from Batteries Plus (manufactured by East Penn), and it has never needed water, going on 3.5 years now.

Should I add "Werker" to the replacement list?

Quote:

what does it matter what the total capacity is? Or how much water people have added? If it needs water, fill it.

It matters, to me, because I'm trying to be consistent across fluids (where it does matter a lot our experience in how much brake fluid you need to buy, for example, for a flush) - and - it matters because I'm trying to create (as always) the best there is in the world by way of summary.

The ONLY way I can do that is to relentlessly ask questions and field the answers from all of you of your combined experience, after having thoroughly combed both the Bentleys and the owners manual for all the details they have.

I also combed the Internet but that can only go so far because I'm looking for E39-specific information to put in the glove box so that, in a pinch, the owner stuck on the side of the road, has all the handy information in a single page.

I am using Deka exact fit (649MF). Has 900 CCA @ 0°F and 1080 CCA @ 32° F.
185Hr reserve capacity and the 20Amp hr rate is 100. Looks identical with the OEM, only black. very happy so far. Here is a link - hit the application guide.

Yes, these are made by East Penn, same as the "Werker" sold at Batteries Plus stores. I am told (but have not confirmed) Batteries Plus continue to sell relabeled/private label East Penn Batteries, but now under the Ray-o-Vac brand name.

The East Penn "Deka" batteries are awesome in performance, and can also be purchased in the Absorbed Glass Mat configuration (AGM) which are totally sealed, never need water (really) and have an even longer life span than typical liquid cell batteries. I believe the standard Deka for E39 sells for around $130 to $140, and the AGM is around $170. But shop around, I found a Batteries Plus store that sold me mine for $93 (three years ago), and the date code on it was recent, only a month or two old.

Interstate. You will not be left stranded. In my Z3 I used to top off the battery with distilled... I just used a paper cup with very little water in it, bent into a "V." The problem is it's very easy to overfill: you're looking down at a nickel-sized white shaft, and determining the actual surface level of the water with any precision is really hard. I always added a little less than up to the fill level, so I didn't go over.

Never refilled my Interstate and don't plan to. I'm not even sure you can open up the cells though I never peeled the sticker off to check

If you follow your chemistry you'll find the reason you add water is because the acid has turned into lead sulfate.. this happens by large current draws across the cells. This causes boiling around the plates which releases the hydrogen gas. The acid water solution is designed to cool these plates as well as provide electron transfer. Natural evaporation occurs as well since evaporation is based around exciting electrons. A cup of water in a room will evaporate even when the room is 50 degreesF. When you add water and then apply electricity, you will increase the acidity and cause the lead sulfate process to reverse. This is why you never have to add acid (in theory). A little cup like at your office water cooler works great. If you squeeze it then it forms a perfect funnel for pouring water into those little holes. Holds almost enough water to top off a cell. DI water is not recomended as it will not support ion transfer but actually inhibit it.

Great. Since this printout is intended to be left in the glove compartment, I'll add a short list of known good replacement batteries (if I can compile that list) so that a (perhaps stranded) driver far from a computer can refer to this list when in need.

DI water is not recomended as it will not support ion transfer but actually inhibit it.

Are you sure? The Bentleys say to use distilled water (see page 020-23 below).

BTW, how does this improved writeup look:

- Battery: A charged battery is 33.5% (volume/volume%) sulfuric acid (4.2 Molar H2SO4, ) & pure water, aka distilled, demineralized, or deionized water (Bentley 020-23) with positive plates containing lead dioxide (PbO2) and negative plates of lead (Pb), both mixed with calcium (Ca) to minimize gassing (i.e., loss of water) and other elements (such as tin, antimony, & selenium to harden the plates and simplify manufacturing) in a polypropylene case. In the discharged state, both plates turn to lead sulfate (PbSO4) as the electrolyte loses its dissolved sulfuric acid and becomes primarily water (which can freeze in cold temperatures and the lead sulfate may form insoluble crystals which, over time, reduce the capacity of the battery if it is not recharged immediately after discharge). [Total Volume: unknown but users have reported adding about 20 ml per cell after two years of use]. Replacement Interval: Lifetime fluid (top off only if needed, after removing steel strap, two stickers and then unscrewing the six cell caps, and filling to the fill line which is 1/4 inch or 5mm above the top of the plates at the very bottom of the internal black plastic depth indicator). The OEM battery has built-in hydrometer where green indicates a charged battery and black indicates a discharged battery, and yellow indicates a defective battery. Better to test at 27°C/80°F by loading battery with 15 amperes for 1 minute (or just turn headlights on w/o engine running) and then perform a 1.265 specific-gravity hydrometer test of each of the six cells (add or subtract 0.004 to the hydrometer reading for every 10°F/6°C above or below 27°C/80°F respectively); and a 12.6 volt open-circuit voltage test across the battery terminals (Bentley 121-5, 121-6). OEM specs are BMW 61.21.8.381.762, USA 729905-10, EN 12V 90Ah 720A, SAE 160 RC 720 CCA. Aftermarket batteries are NAPA #7549, Deka 649MF, Interstate MTP-93, Werker model???, Batteries Plus model???, East Penn model??? (need specific model info) with a stamped date code within the last month or two.

Donna, my OEM battery was always maintained, and I was pleased with it. However, this very early spring (March), the FSU repeatedly discharged it, eventually killing it. It would not hold the charge anymore - explained by your Bentley blurb attached (it was NOT immediately recharged, because as you know the FSU works in mysterious ways when it fails. Sometimes it would start fans and whatnot, other times it would stay put. In the final stages of failure, the FSU will drain steady the battery aka keep fans on all the time and other stuff). After the damage was done, when I recharged my old battery the 3d and 4th time in 10 days or so, she would not hold the charge at all. Barely starting the car. However it lasted 7 years. I'm OK with it, as usually a battery would last 5 years if you're lucky (I know people have reported phenomenal 11 years of service life out of the OEM BMW battery - Varta- but maybe their FSU was replaced before it went kaputt?

In your case, it could be that the insoluble compounds formed while the battery was discharged by the FSU and then never went back into solution. The battery was, in essence, merely water instead of electrolyte.

I wonder if pouring sulfuric acid in at that point would have resurrected your dead battery that won't hold a charge?

I honestly don't know. I did not dwell on that subject. If all that was left as fluid was "water" I would not know, and i would not taken any chance of draining the battery and replacing the fluid with the correct acid concentration. Might have worked. I don't know. But again, you don't know what that acid concentration in the "watery" solution is. You try to dump it thinking it's water, you spill a bit, and then you realize it was actually potent acid. At that age of the battery, it's maybe safe to get a new one and be done with it. I dunno?

FWIW, I do not believe you can "restore" a dead battery. I don't know the chemistry behind it but starting batteries are designed to stay at full charge to maximize lifespan. Repeated discharging of a starting battery will kill it. That is why they are not used on boats that use trolling motors, fish finders, etc. when the main motor is not running. For repeated discharging of a battery, a deep cycle battery is recommended, which can sustain repeated discharges and will recharge to it's full potential.

In my e38 the dealer unscrewed the holes in the battery and never recapped it. I had to buy a new one because the battery was destroyed (luckily it somehow didn't do any noticable damage to the trunk). That battery lasted about 7 years before this happened. In my e39 I had to replace the battery within a few months of ownership. I don't plan on every checking the fluid levels.... -Steve

Are you sure? The Bentleys say to use distilled water (see page 020-23 below).

DI water = deionized

as far as batteries, I just bought an interstate MTP-93

ran me $135 from the interstate shop and they installed it (warehouse not local chain); they tested my old one and it was still producing 350CCA and 12.5V, told me it was installed 3/2000 which means that battery lasted 10 years and the BMW battery only lasted 3 1/2-4 (9/96 build date).

I added water to the old battery prior to swapping it, it saved it a little (was reading 100CCA and 11.5V immediately after turning off the car). don't know exactly how much water it took, probably 1/8-1/4 of a gallon. the interstate you lift the handle and then pop open the rectangular piece under the handle to expose 3 cells (each side). mine was quite low, all but 1 cell was exposed and 2 were completely dry.

Ok I took another look at your picture and noticed that you laid the ratchet across the CABLES after they have been disconnected. This is fine. I thought you were laying it across the POSTS. Don't ever do that, the wrench will immediately turn red hot and you'll be badly burned as it will melt your hand to the wrench. But you didn't do that, it's just what my eyes saw. Phew!!!!